JPH06142672A - Microorganism immobilizing carrier - Google Patents

Abstract

PURPOSE:To obtain the microorganism immobilizing carrier which can shorten a taming period for a microorganism, and also, can manufacture simply the carrier, and moreover, can improve the reaction efficiency by allowing a hydroxyapatite compound substance to adhere onto the surface of a carrier base material consisting of a synthetic resin. CONSTITUTION:The microorganism immobilizing carrier 9 is used by being suspended by a biological reaction treatment tank for treating sewage biologically, and used for allowing a fungus body (microorganism) to adhere (tame). In this case, by allowing hydroxyapatite compount substance B to adhere onto the surface of a carrier base material A consisting of a synthetic resin, the microorganism immobilizing carrier 9 is constituted. Also, the carrier base material A is formed in a sponge-like porous body, etc. Moreover, by forming the carrier base material A by a synthetic resin whose specific gravity is <=1, the specific gravity of the microorganism immobilizing carrier 9 to which the hydroxyapatite compount substance B is allowed to adhere is adjusted to 1.0-1.1. In such a way, a taming period for the microorganism is shortened, and also, the microorganism immobilizing carrier 9 is manufactured simply, and moreover, the reaction efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for immobilizing microorganisms, and more specifically, it is used for immobilizing microorganisms by suspending sewage such as sewage, wastewater and human waste in a biological reaction treatment tank for biological treatment. The present invention relates to a carrier, which is a carrier on which microorganisms (that is, microorganisms) adhere, on which a microorganism is immobilized.

[0002]

2. Description of the Related Art Various methods are known as methods for treating sewage such as sewage and waste water, but biological treatment methods utilizing the purification function of microorganisms are the most common. The biological treatment method includes an aerobic method in which air is blown into a biological reaction treatment tank (hereinafter referred to as a treatment tank) and an anaerobic method in which air is not blown.

As a method for contacting microorganisms with pollutants in wastewater in the treatment tank, a method of suspending the microorganisms in a floc shape is generally adopted. The microorganism suspension method is generally called an activated sludge method, and in order to improve reaction efficiency, as shown in FIG. 6, a sludge 6 settled in a subsequent settling tank 4, that is, a part of the activated sludge 6 containing microorganisms is treated in a treatment tank 2 It will be returned to. However, if the amount of returned sludge is increased, the settling property of the sludge 6 in the settling basin 4 deteriorates. Therefore, the amount of returned sludge is limited. Therefore, the concentration of the sludge 6 in the treatment tank 2 is limited to about 3000 ppm or less, and the treatment of wastewater Cannot be performed efficiently (the residence time becomes long). Therefore, recently, as illustrated in FIG. 5, a microorganism immobilization carrier of a predetermined size that can be separated by a simple screen 15 or a microorganism immobilization carrier 17 that can be separated by specific gravity or magnetism is suspended in the treatment tank 2. Attempts have been made to make the solution turbid, thereby increasing the concentration of microorganisms to increase the efficiency of biological reaction and facilitating solid-liquid separation. Such a method can also be applied to the anaerobic method.

The removal of organic substances is possible by either aerobic method or anaerobic method. However, removal of ammonia nitrogen requires aerobic nitrification (ammonia nitric acid, nitrite) and anaerobic denitrification (decomposition of nitric acid and nitrous acid to nitrogen gas), and these are responsible for these reactions. Since the nitrifying bacteria and denitrifying bacteria have a slower growth rate than the BOD component oxidizing bacteria, in the standard activated sludge method for removing BOD components, the surplus bacteria are extracted from the settling tank 4 as shown in FIG. It flows out as sludge, and therefore the concentration of nitrifying bacteria and denitrifying bacteria required in the denitrification tank 7 and the nitrification tank 8 of the treatment tank cannot be maintained. Therefore, it is necessary to take measures such as prolonging the residence time of the above-mentioned bacteria, and as a method therefor, there is a so-called activated sludge circulation modification method for removing nitrogen. In total, the average time is 16 hours, which is about twice that of the standard activated sludge method. It has been attempted to suspend the microorganism-immobilized carrier also in the denitrification tank 7 and the nitrification tank 8 of the modified activated sludge circulation method to improve the reaction efficiency.

Conventionally, as the above-mentioned microorganism-immobilized carrier, a method by a comprehensive immobilization method in which microorganisms are synthesized so as to be confined in a plastic gel before being put into a treatment tank (hereinafter referred to as comprehensive-immobilized carrier), There is a method by a binding method for attaching microorganisms to the surface of particles in a treatment tank (hereinafter referred to as a binding type carrier). PV for the gel of the comprehensive immobilization method
A and PEG are often used. Particles or carriers used in the binding method are plastic particles or specially processed to improve the ability of microorganisms to be supported on the surface (mainly for screen separation method), sand, activated carbon, blast furnace slag, ceramics (for sedimentation separation method). ), Or magnetite (for magnetic separation method). Incidentally, after the bound carrier (particles) is put into a treatment tank, microorganisms adhere to the surfaces of the particles and are immobilized.

The entrapping immobilization type carrier or the binding type carrier is put into a treatment tank and suspended for use. At this time, the surplus sludge is discharged from the treatment tank to the outside of the tank by sedimentation and removal, but a part of the sedimentation sludge is returned to the treatment tank so that the sludge and the carrier are mixed, and In some cases, some of the existing sludge is used without returning it.

[0007]

However, in the above-mentioned conventional microorganism-immobilized carriers, in the case of the bound carrier, it usually takes 2 to 3 weeks for adhesion (acclimation) of the microorganisms after being added to the treatment tank, and it takes a long time. There is a problem that it requires. As a countermeasure against this, it is necessary to use a carrier (particles) to which microorganisms are easily attached to shorten the acclimation period, but in this case, special processing such as forming irregularities on the surface of the carrier (particles) is required, and the carrier is not manufactured. There is a problem that it is very difficult, requires a long time for its production, and causes a significant decrease in economic efficiency.

On the other hand, in the entrapping immobilization type carrier, the manufacturing process of the carrier is complicated, and it is difficult to stably immobilize the microorganisms because the microorganisms are involved in the gelling process of the polymer. There is a problem that the characteristics tend to be unstable. In addition, special measures such as preservation are required.
In addition, although the inside of the carrier also contains microorganisms, when actually applied to wastewater treatment, the microorganisms adhere to the surface of the carrier and become deficient in the inside of the carrier and pollutants (nutrient source of microorganisms). However, the microorganisms on the surface of the carrier are substantially effective, and the microorganisms inside the carrier do not work so much, and thus the reaction efficiency is low.
As a countermeasure against this, it is considered that the carrier (gel) has a sponge-like porous structure, but this is extremely difficult and difficult to realize.

The present invention has been made by paying attention to such a situation, and an object thereof is to solve the problems of the above-mentioned prior art and to make the surface of the carrier uneven or the like as compared with the conventional bonded carrier. The acclimation period (adhesion period of microorganisms after being put into the treatment tank) can be shortened without performing any special processing, and the manufacturing process of the carrier is simpler than the conventional entrapping fixed carrier. Another object of the present invention is to provide a binding-type microorganism-immobilized carrier which can have a sponge-like porous structure and can improve the reaction efficiency.

[0010]

In order to achieve the above object, the microorganism-immobilized carrier according to the present invention has the following constitution. That is, the microorganism-immobilized carrier according to claim 1 is a microorganism-immobilized carrier characterized in that a hydroxyapatite-based substance is attached to the surface of a synthetic resin carrier substrate.

In the microorganism-immobilized carrier according to claim 2, the synthetic resin carrier substrate is a sponge-like porous body, a fiber assembly, or a hollow cylindrical body or a granular body. It is a carrier for chemical conversion. Further, in the microorganism-immobilized carrier according to claim 3, by forming the carrier substrate with a synthetic resin having a specific gravity of 1 or less, the specific gravity of the microorganism-immobilized carrier after the hydroxyapatite-based substance is attached is 1.0 to 1.1. Adjusted claim 1
Alternatively, the microorganism-immobilized carrier according to item 2.

[0012]

As described above, the microorganism-immobilized carrier according to the present invention comprises a hydroxyapatite-based substance attached to the surface of a synthetic resin carrier substrate. Therefore, the carrier surface has a coating layer of a hydroxyapatite material.

By the way, apatite is A ₁₀ (MO ₄ ) ₆ X ₂
It is a crystalline substance having a chemical composition represented by. However, in the composition, A is a monovalent cation such as Ca or Ba, and M is
P, As, Si, etc., X is F, OH, Cl, etc. The hydroxyapatite-based substance is a typical substance among the above-mentioned apatites, and is a crystalline substance in which X is OH and has a chemical composition of A ₁₀ (PO ₄ ) ₆ OH ₂ .

The above-mentioned hydroxyapatite-based substance basically has a property that it is extremely excellent in affinity with microorganisms and is well compatible with microorganisms. Therefore, attachment of microorganisms is very likely to occur. The microorganism-immobilized carrier according to the present invention has a coating layer of such a hydroxyapatite-based substance on the surface, and therefore, it is very easy for microorganisms to adhere to the coating layer of the hydroxyapatite-based substance on this surface, Therefore, the acclimatization period (the period of attachment of microorganisms after being placed in the treatment tank) can be significantly shortened without subjecting the carrier surface to special processing such as unevenness.

In addition, in the microorganism-immobilized carrier according to the present invention, the carrier base material on which the hydroxyapatite-based material coating layer is provided is made of synthetic resin, and the synthetic resin is excellent in corrosion resistance and processability, so that durability is improved. In addition, various shapes such as sponge-like porous bodies can be obtained. Further, it can be produced by coating the surface of a carrier substrate with a hydroxyapatite-based substance, and the coating can be carried out by a method of immersing the carrier substrate in the hydroxyapatite-based substance. In comparison with, the manufacturing process of the carrier is extremely simple.

Therefore, the synthetic resin carrier substrate can be made into a sponge-like porous body, a fiber assembly, or a cylindrical hollow body or a granular body, and in this case, the ratio of the hydroxyapatite-based material coating layer is increased. The surface area (ratio of the surface area to the unit weight of the carrier) can be increased, so that the reaction efficiency of the microorganism-immobilized carrier in the treatment tank can be further improved.

Here, when the carrier base material is a sponge-like porous body, the inner surface of the pores can be coated with the hydroxyapatite-based substance. Such a microorganism-immobilized carrier, after being introduced into the treatment tank, has contaminants (: nutrient sources for microorganisms) that also penetrate into the pores of the carrier, so that microorganisms adhere to the inside of the carrier.
The microorganisms inside the carrier also work effectively and the reaction efficiency is increased.

Various kinds of synthetic resins can be used as the carrier base material. Therefore, the specific gravity of the carrier substrate is 1
When formed of the following synthetic resin, the specific gravity of the microorganism-immobilized carrier after the hydroxyapatite-based substance can be adjusted to 1.0 to 1.1. Then, the specific gravity of the microorganism-immobilized carrier becomes almost the same as that of wastewater. The suspended state in 1 is further improved, and thus the biological reaction efficiency can be improved more reliably.

The microorganism-immobilized carrier according to the present invention is a binding-type carrier, which allows microorganisms (bacteria) to adhere (acclimate) in the treatment tank during use, that is, after being added to the treatment tank. Since the bacterial cells are not retained in advance at the time of production, the carrier can be easily managed (stored and stored), and no special measures are required for storing the carrier.

The resin of the synthetic resin carrier substrate is not particularly limited, and examples thereof include urethane, polypropylene and the like, expanded polypropylene, expanded polyethylene, expanded ABS.
Etc. can be used.

Regarding the shape of the synthetic resin carrier substrate, a non-woven fabric or the like can be used as the fiber aggregate, and further, a brush-like one as shown in FIG. 2 is also included. The sponge-like porous body includes not only a sponge-like porous body but also a natural or synthetic hemp. The shape of the granular or sponge-like porous material is not particularly limited, and various shapes such as spherical and angular can be used, but the size is 3 to 100 mm square or 3 to 100 mm.
It is desirable to make it about φ. If it is less than 3 mm, it is difficult to separate it with an ordinary simple screen, and if it exceeds 100 mm, the fluidity is deteriorated. 3-20 from the point of the liquidity
About mm is more desirable.

As the hydroxyapatite-based substance, A ₁₀ (P
Any compound having a chemical composition of O ₄ ) ₆ OH ₂ (A is a cation having a valence of 1 to 3) may be used. For example, one having a chemical composition of Ca ₁₀ (PO ₄ ) ₆ OH ₂ can be used.

The amount of the microorganism-immobilized carrier according to the present invention loaded into the treatment tank may be determined depending on the type of carrier (shape, size, etc.), the type of wastewater to be treated, the purpose of treatment, etc., but is not particularly limited. It is desirable that the volume ratio (the ratio of the carrier to the volume of the processing tank) be 5 to 40%. At about 40%, as shown in Fig. 4, for example, a considerable portion of the tank is occupied by the carrier, and the carrier fluidity can still be secured, but at more than 40%, the carrier fluidity deteriorates. If it is less than 5%, the absolute surface area of the carrier is small,
This is because the effect of increasing the efficiency of biological reaction is usually small.

[0024]

[Example] As the synthetic resin carrier substrate, industrially produced polypropylene particles having a particle size of about 3 to 5 mm were used. As the hydroxyapatite-based substance, one having a chemical composition of Ca ₁₀ (PO ₄ ) ₆ OH ₂ was used. As shown in FIG. 1, the hydroxyapatite-based substance B was adhered to the surface of the carrier substrate A (polypropylene particles) and the specific gravity was adjusted to 1.03 to fix the microorganisms for denitrification according to the embodiment of the present invention. The carrier 9 was obtained.

A synthetic resin sponge (ether polyurethane foam) produced industrially is used as a carrier substrate, and the surface of the sponge skeleton has the same hydroxyapatite-based material [Ca ₁₀ (PO ₄ ) ₆ OH ₂ ] was adhered to obtain a microorganism-immobilized carrier for nitrification according to an example of the present invention. The production of these microorganism-immobilized carriers can be performed extremely easily as compared with the conventional entrapping immobilization type carriers.

These microorganisms-immobilized carriers were used by suspending them in a treatment tank of a wastewater treatment plant operated by a modified activated sludge circulation method for the purpose of removing organic matters and ammonia nitrogen. The details will be described below with reference to FIG.

The denitrification tank 7 in the treatment tank was charged with the above-mentioned denitrification microorganism-immobilized carrier 9 and the nitrification tank 8 was charged with the above-mentioned nitrification microorganism-immobilized carrier 10 in a volume ratio of 20%. . The operation method is the same as when the carrier is not added, and the sewage primary treated water 1 is first introduced into the denitrification tank 7 and then into the nitrification tank 8. Screens 11 and 12 for preventing carrier outflow are provided at the processing outlets of the tanks 7 and 8. Further, the denitrification tank 7 is provided with an underwater agitator 13 for agitating. The nitrification tank 8 is provided with an air diffuser 14 for stirring and supplying oxygen.

Since the nitrification tank 8 is operated by an aerobic method, ammonia in the sewage primary treated water is converted into nitric acid by nitrifying bacteria, and BOD components are oxidatively decomposed by BOD oxidizing bacteria. A part of the nitrification solution that has passed through the screen 12 from the nitrification tank 8 is returned to the denitrification tank 7 through the nitrification solution circulation line 16. The return flow rate is usually about 100 to 200% of the amount of the sewage primary treated water 1 introduced into the denitrification tank 7.

The nitrification liquid, that is, nitric acid, returned to the denitrification tank 7 is decomposed into nitrogen by denitrifying bacteria in the presence of organic substances in the sewage primary treated water 1 flowing into the denitrification tank 7. Here, the ammonia in the sewage primary treated water 1 is contained in the outflow water from the denitrification tank 7 without change because the denitrification tank 7 is in an anaerobic state, and is introduced into the nitrification tank 8 through the screen 11. It On the other hand, the remaining treated water that has flowed out of the nitrification tank 8 is introduced into the settling basin 4 and separated into treated water (supernatant water) and excess sludge (bottom drawn sludge).

When the treatment operation as described above was carried out, the denitrifying microorganism-immobilized carrier 9 according to the embodiment of the present invention, and
The microorganism-immobilized carrier 10 for nitrification has a predetermined denitrification function,
Also, it was confirmed that the time until the nitrification function is expressed is within one week, and the acclimation period can be significantly shortened as compared with the conventional bound carrier.

Further, the treatment effect is almost the same as that in the case where the carrier is not added (BOD component and nitrogen removal effect).
The volume of the treatment tank is 1 / both for denitrification tank 7 and nitrification tank 8
It was also confirmed that it can be reduced to 2 to 1/3.

[0032]

EFFECTS OF THE INVENTION The present invention has the above-mentioned constitution and functions, and the microorganism-immobilized carrier according to the present invention has a special treatment such as unevenness on the surface of the carrier, as compared with the conventional bound carrier. The acclimation period (adhesion period of microorganisms after being added to the treatment tank) can be shortened even without performing the treatment, and the carrier production process is simpler and sponge-like compared to the conventional entrapping fixed type carrier. It has an effect that a porous structure can be obtained and reaction efficiency can be improved. Furthermore, since it is a binding type carrier, there is an effect that no special measures required in the case of the entrapping immobilization type carrier are required when the carrier is stored.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of a microorganism immobilization carrier for denitrification according to an embodiment of the present invention.

FIG. 2 is a diagram showing an appearance of a brush-shaped carrier base material according to the present invention.

FIG. 3 is a diagram showing an operating condition of wastewater treatment using the microorganism-immobilized carrier according to the example of the present invention.

FIG. 4 is a diagram showing a state in which the volume ratio of the microorganism-immobilized carrier in the treatment tank is 40%.

FIG. 5 is a view showing a state in which a conventional microorganism-immobilized carrier is suspended in a treatment tank.

FIG. 6 is a diagram for explaining a conventional standard activated sludge method.

FIG. 7 is a diagram for explaining a conventional modified activated sludge circulation method.

[Explanation of symbols]

1--sewage primary treated water, 2--treatment tank, 3--air,
4--sedimentation tank, 5--treated water, 6-sludge,
7--denitrification tank, 8--nitrification tank, 9--denitrification microbial immobilization carrier, 10--nitrification microbial immobilization carrier, 11, 12--screen, 13--water stirring device,
14--Aeration device, 15--Screen, 16--Nitrification liquid circulation line, 17--Microorganism immobilization carrier, A--Carrier substrate,
B--A hydroxyapatite type substance.

Claims (3)

[Claims] 1. A microorganism-immobilized carrier comprising a synthetic resin carrier substrate and a hydroxyapatite-based substance attached to the surface thereof. 2. The microorganism-immobilized carrier according to claim 1, wherein the synthetic resin carrier substrate is a sponge-like porous body, a fiber assembly, or a cylindrical hollow body or a granular body. 3. The specific gravity of the microorganism-immobilized carrier after adhesion of the hydroxyapatite-based substance is adjusted to 1.0 to 1.1 by forming the carrier base material with a synthetic resin having a specific gravity of 1 or less.
Alternatively, the microorganism-immobilized carrier according to item 2.